differance between a 5"/51 caliber and a 5"/38 caliber naval gun

The 5"/51 has a longer barrel than the 5"/38.  The 5"/51 barrel is 21' 3" long, the 5"/38 barrel is almost 16' long.  To figure barrel length, multiply the gun sheel (5") by the caliber size (51 or 38 for our example), and divide by 12.    The barrel length is from the muzzle to the breech block, and is longer than the amount of barrel sticking out of the turret.

For naval guns, the caliber measurement is the barrel length expressed as multiples of the barrel bore diameter

The barrel length of a 5"/38 is 190 inches.  The barrel length of a 5"/51 is 255 inches.   In scale, the difference in the barrel lengths between the two guns  is almost 0.2 inches (0.185").   That length difference is significant and noticeable in that scale.    Additionally the gun mount configuration is different between the two guns.  

Accurate?  IMO no, but it is you model and you may complete it anyway you see fit to your own definition of accuracy.

You may want to locate a copy of Friedman's "US Naval Weapons" it has some line drawings that will show the differences.   You may also be able to scratchbuild a gun and make resin copies.

 

Here is a link to a Web Site with info on US Naval guns, mounts & ammunition.

http://www.navweaps.com/Weapons/WNUS_Main.htm

Hank:

From a modelling perspective, the biggest difference between the two mounts is that the 5"/51 was a single purpose anti-surface weapon with a low degree of elevation (and mounted closer to the deck) while the 5"/38 was a dual purpose weapon intended to be used for both anti-surface and anti-air and had to be able to elevate higher.

I don't know that the difference in the length of the gun barrels would be noticeable in 1/350 except to someone very familiar with the two weapons.  The most noticeable feature, to my eyes, would be the width of the gun barrel which should be the same between the two weapons.  Since the 5"/51's were mounted inside casemates on the older BB's, differences in the mounts and breach mechanisms for the two guns would probably not be visible on your model.  You just need to make sure that you can get the 5"/38 close enough to the deck so that the gun is not butting up against the deck over the casemate.

Hope this helps,

 Mike 

i am twisting this subject slightly but  what is the rate of fire on the 5/38  to me it would seem a bit slow against an aircraft flying by you at 300 plus mph

The 5"/38 had a rate of fire of 15 - 20 rounds per minute per barrel.   This is part of the reason why the Sumners and Gearings, with fewer gun mounts but more gun tubes, were armed as they were.  .

While the gun was capable of local control, it was most often used under the automatic control of a radar-guided fire control system, such as the MK37 on the Fletchers.

In addition, the 5" shell was capable of being fuzed by a VT proximity-type fuze. This would allow the shell to burst when it past within a lethal range of a target.

The 5-inch guns were considered to be a very successful weapon and were used into the '70s.

 

I think Ed's point is essentially correct, the 5"/38 was effective against aircraft when using VT fuses with multiple barrels that were radar-guided with the firing solution being generated by an electro-mechanical calculator (in 1944/45 it was probably considered a computer, but that's a stretch by modern standards).  Even so, DD's on radar picket duty were often in grave danger of being overwhelmed by more targets than they could engage.

The 5"/38 was a formidable weapon, but 15-20 RPM per barrel just wasn't enough to handle a wave of Kamikaze attackers.  On the other hand, the 20mm mounts had a high rate of fire but were also considered ineffective with the 40mm mounts being a good compromise between the two.  By 1945 the USN had begun to deploy the open twin 3"/50 mount that had a higher rate of fire than the 5"/38 and more hitting power than the 40mm quads and twins.

You have to wonder how any aircraft were shot down in the early years of the war.  The old BB's at Pearl Harbor typically had four 5"/25 mounts in each broadside battery that were guided by a director that (if I recall directly) could not track engage targets with speeds in excess of 200MPH.  The shell fuses were set mechanically at the mount based on information from the director, loaded and fired.

Mike